This invention relates to a synthetic resin matrix system which can be embodied with select drugs and chemicals and provide suitable storage for extended and sustained duration release of the embodied agent from the matrix system following various modes of administration.
According to the literature (Madan, Pharmaceutical Manufacturing, April, 1985), approximately fifty major pharmaceutical companies are engaged in the production and marketing of about 200 sustained-release drug delivery products which represent about five percent of the total pharmaceutical products sold. A survey of this literature shows that various methods have been used to fabricate these drug products. Most of the methods develop a series of protective layers of inert substance which encapsulate the drug and utilize dissolution as the rate-limiting step in controlling the release of the active ingredient from the dosage form. Because a drug form with a low dissolution rate of the overlay is slowly released, the main thrust of the development of sustained-release delivery systems has been directed toward drugs that are highly water soluble. However, the solubility of such drugs can be changed by several methods.
Orally administered extended release drug delivery systems presently available or under development employ a variety of release mechanisms ranging from: (1), enteric coating; (2), beads or spheres; (3), enteric coated beads or spheres; (4), repeat action tablets; (5), mixed release granules; (6), erosion cores, with and absent of initial dose; (7), ion exchange; (8), microencapsulation; (9), the osmotic pump; and (10), matrix tablets.
Blank and Fertig (U.S. Pat. No. 3,927,206), disclosed that copolymers comprising acrylic or methacrylic acid and methyl methacrylate, neutralized by the addition of cyclic alkylene imines, preferably ethylene imine, form a product which is capable of absorbing large amounts of material soluble in water, and slowly releasing those materials. The treated copolymers are particularly useful in the formation of contact lenses for the application of medicinals to the eye and for other depot materials.
Pedersen (U.S. Pat. No. 3,954,959), claimed an oral drug preparation having a protracted effect and a substantially constant rate of release of the drug, comprising an admixture of a drug and an effective amount of a buffer acid, buffer acid salts, and mixtures thereof, in the form of small spheroidal particles of 0.1 to 5.0 mm diameter, said particles having a coating thereon of an acrylic polymer film permitting drug diffusion. The dragee lacquer, thus formed, allows for diffusion of the stomach and intestinal juices through the coating, the coating not being soluble in said juices.